The present invention relates in general to a scroll type compressor and more particularly to a scroll type compressor having bottom plates disposed at bottom portions of confronting scroll members.
With reference to FIG. 1, description will be made as regards a conventional scroll type compressor designated by a reference numeral 50. The scroll type compressor 50 comprises a casing 11 and, in the casing 11, a movable scroll member 20 and a fixed scroll member 30 which have involute members 21 and 31 and end plates 22 and 32 integral with the involute members 21 and 31, respectively. In other words, the movable and the fixed scroll members 20 and 30 have involute grooves which are defined by the involute members 21 and 31 and end plates 22 and 32, respectively. The movable and the fixed scroll members 20 and 30 are engaged with each other in a confronting relation with their involute curves offset at 180 angular degrees with each other. As a result, a plurality of compression spaces are defined between the movable and the fixed scroll members 20 and 30.
The fixed scroll member 30 is fixed in the casing 11. The movable scroll member 20 is unrotationally but orbitally movably supported, in a front housing 14, on the side opposite to the side of the involute member 21 of the end plate 22 through a rotation-preventive mechanism 15. So that, the movable scroll member 20 provides an orbital motion along its orbital way. A boss portion 23 in the form of projection is disposed nearer to the central portion of the end plate 22 of the movable scroll member 20. An eccentric bush 17 of the driving mechanism is disposed through a drive bearing 18 to permit a orbital motion of the movable scroll member 20.
The driving mechanism comprises an enlarged portion 40b disposed at an end of the driving shaft 40a, an eccentric pin 40c disposed on the opposite side of the driving shaft 40a of the enlarged portion 40b, and an eccentric bush 17 for permitting the eccentric pin 40c to extend through the eccentric portion. The boss portion 23 serves to rotatably support the eccentric bush 17 through the drive bearing 18.
When the movable scroll member 20 is orbitally moved, a fluid is sucked in each compression space and is compressed by the revolution-preventive, orbital motion of the movable scroll member 20 relative to the fixed scroll member 30 with movement to a central portion of the involute members 21, 31. Thereafter, the fluid is discharged from the discharge hole 33 disposed at a center of the end plate 32 into a discharge chamber 39.
In the scroll compressor 50, a drive bearing 18 is press-fitted to the central portion of the end plate 22 of the movable scroll member 20. It is assumed that this press-fitting of the drive bearing 18 causes the movable scroll member 20 to generate bending or warping which corresponds to the press-fitting force. The bending or warping produces a gap between each of the involute members 21 and 31 and each of the end plates 22 and 32. The gap is increased at a central portion than at the other outer circumferential portions. Therefore, a sealing effect to each compression space decreases at the central portion of each of the scroll members 20, 30 to result in reduction of a discharging capacity and generation of noises due to blow-by gas of the fluid.
An attempt was made to provide tip seals 51 and 61 having a larger thickness at the central portions thereof than the other portions. But, it is found that if the thickness of the central portions is larger than required, it permits the fluid to accidentally flow along the side surface of the tip seals 51 and 61 to generate blow-by, resulting in reduction of discharge capacity.